Device at telecommunications systems using a pattern of time slots

ABSTRACT

A radio based access network type Digital European Cordless Telecommunication DECT in which powerful and simply-built up network components, such as repeaters are an integral part. The device makes possible a signaling which makes digital decoding and adding a special capacity to the system unnecessary.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention is intended to be used at telecommunicationsystems, for instance radio based access networks in which powerful andsimply constructed network components, preferably repeaters, areincluded.

2. Discussion of the Background

The present invention shows how signalling can be superimposed onexistent DECT Digital European Cordless Telecommunications-signalling.The invention can also be used on other systems with similar accessmethod as DECT.

DECT uses TDMA/TDDD/MC, i.e. Time Division Multiple Access/Time DivisionDuplex/MultiCarrier, which is schematically shown in FIG. 1, whichillustrates the division and use in time and frequency in DECT. Alongthe x-axis is shown a frame consisting of 12+12 time slots for down anduplink respectively, and along the y-axis is shown the 10 carrierchannels, i.e. the division in frequency. In DECT these slots may beutilized very freely; because DECT is intended to be selfplanning etcthere are no real obstructions for using all the slots in a frame for,for instance a down link.

TDD in classification in up and down link on the "same" carrier and MCin the using of more than one carrier. The TDMA-structure can be said tobe in the division in time slots for up and down link.

The technical problem consists of the fact that there for some servicesare needs for sending short messages within a DECT-system withoutneeding to allocate a special time slot for this and without the need toallocate more frequency space.

With a DECT-system is in this connection referred to Fixed Parts (FP; anFP can consist of a CFP, Central Fixed Part and one or more remote fixedpart RFP. RFP and or FP can be described as "base stations" in DECT),Repeaters (sometimes called FR; Fixed Repeaters) and Portable Parts(PP). With short messages is referred to a short string of charactersintended for for instance identification (of base stations repeaters orother radio based network elements) etc, or special messages of forinstance broadcast type. Some of the equipment which can receive ortransmit these messages shall be simple, and is not intended to containany digital signal processing of the contents in separate time slots(typical examples of this are repeaters).

SUMMARY OF THE INVENTION

By the invention can be built up arrangements with powerful and simplenetwork components, which shall be able to signal without digitaldecoding. For instance radio based access networks with repeaters usingTDMA/TDD/MC are appropriate for implementation of the invention. Theamount of information which can be transferred with the invention isvery large, which implies that even a more general communication will bepossible. By the invention is signalling between network componentswithout mentioned digital decoding or adding separate capacity madepossible. The new procedure of sigalling is not previously known.Repeaters can be arranged in a functional and simple way, which givesthe mentioned system a very big economic and functional potential. Theinvention can be used for present systems using mentioned TDMA/TDD/MC.By the invention are solved important problems related to systemsignalling to respective from repeaters in TDMA/TDD/MC-system withoutthe communication being negatively influenced.

BRIEF DESRIPTION OF THE DRAWINGS

One at present suggested embodiment of a device which presents thesignificant features of the invention is described in the following atthe same time referring to the enclosed drawings, where;

FIG. 1 schematically shows the time and frequency division in DECT,

FIG. 2 shows a graphic description of the superimposed signalling,

FIG. 3 shows superimposed signalling with using whole and half timeslots, and

FIG. 4 shows superimposed signalling with using two transceiverssimultaneously.

DISCUSSION OF THE PREFERRED EMBODIMENT

The pattern representing the TDMA/TDD/MC-signalling can as such be usedfor superimposed signalling. In the case of DEC this allows for a simplecase 10¹² different possibilities (messages which by that becomemaximally as long) if only up or down links are used, 10²⁴ if both areused. How this signalling is performed is shown in FIG. 2.

In each time slot there are 10 different possibilities (carrierchannels), within a frame (a frame consists of 12 time slots for uplink,and 12 time slots for downlink) can then be achieved totally 10¹² (ifonly either uplinks or downlinks is used) or 10²⁴ (if both uplinks anddownlinks are used).

The contents in a time slot can be speech or data, but the contents canof course also be "empty", i.e. the slot is sent, but there are nouseful information in the slot itself. With this arrangement thecapacity of the system is not lowered at all, no changes within the timeslots are needed, etc.

It is possible to increase the signalling possibilities further:

a) use "halfslot" (is defined in the DECT-standard), which givespossibility to separate different messages from each other (one class ofmessages only uses halfslots for instance) or can be used to increasethe "word length" (or the number possible) in the message. In FIG. 3 isdescribed how ordinary slots are combined with halfslots. In this casethere are consequently three different possibilities in a time andcarrier slot (a specific square in the diagram in FIG. 3); empty, fullor half.

For each time slot (a specific column of squares in the diagram) thisgives 20 different possibilities. For a frame this consequently gives20¹² or 20²⁴ different possibilities (only up and down link, respectiveboth up and down link).

b) With more than one transceiver per "party" the number of possiblemessages (and the word length in these) are dramatically increased: withtwo transceivers per equipment the number of combinations is 90¹² wheneither up or down link is used, and 90²⁴ when both up and down links areused.

In a specific time slot (i.e. column in the diagram in FIG. 4) there are10 different possibilities for the "first" transceiver, and 9 differentpossibilities for the second, totally 90 different possibilities pertime slot. (The transceivers cannot send on the same frequency at thesame time, for the superimposed signal as such this should be noproblem, but it is not allowed according to the DECT-standard, and itwould also be pointless).

The combination of a) and b) above is of course possible, and especiallyinteresting in the case when only the base stations in the DECT-systemhave more than one transceiver; quite different messages can be sent outsimultaneously without influencing each other.

As a conclusion can be established that the present invention givespossibility to via "normal" DECT-structure transfer many independentcomparatively long messages without the capacity being influenced or theneed for using or analyzing the contents in any time slot.

The DECT-standard is so designed that, for duplex communication, it isthe portables that select what base station, carrier frequency and timeslot shall be used. However, the base stations shall approve of theportable's channel choice. On other hand, for simplex communication, thebase station can both select and approve of channel.

This entails that a base station (Fixed Part) can allocate time slots,which in its turn implies that the here suggested method of signallingin principle can be used by a base station according to presentstandard. Performance for superimposed signalling probably will increaseif the base stations are given possibility to select channel straightlyalso for duplex communication. It is, however, probable that some kindof changing of the standard is coming, among other things justified bythe introduction and standardization of repeaters which must be able toprove their identity to the base station in question.

Detecting of superimposed signalling is performed according to thefollowing:

For systems where each transceiver can only listen in to one channel pertime slot (for instance DECT), the invention comprises the followingadditions which make possible detecting of superimposed signalling:

A message shall be repeated during as many consecutive frames as thenumber of carriers which are needed to create the message. The receiverlistens in to one and the same carrier during a time frame. At the nextframe the next carrier is listened in to. This is repeated until allcarriers have been listen in to.

For DECT this implies that a message has to be sent continuously during10 frames, i.e. 100 ms. Further the receiving transceiver must listen into the carriers in a cyclic way as above. Cyclic listening is defined inthe DECT-standard and is called "primary scan". The principle isconsequently possible to realise within the present DEC-standard.

For system (for instance DECT) where the transmitter of a message knowswhich cycle of listening the receiver is using, the whole message neednot be repeated during each frame. It is sufficent to send that part ofthe message which is created on the carrier which is listened in to forthe moment. In this way the amount of signalling is decreased.

The invention is not confined to the in the example above shownembodiment but may be subject to modifications within the frame of thefollowing patent claims and the invention idea.

We claim:
 1. A communication device in a telecommunication system,comprising:a short-message signaling mechanism configured to send ashort message superimposed on an existing Digital European CordlessTelecommunications, DECT, signal without having allocated thereto adedicated time slot or extra frequency space for the short message, saidshort-message signaling mechanism including a TDMA/TDD/MC-signalingmechanism configured to convey the short message in a pattern of timeslots superimposed on the DECT signal.
 2. The device of claim 1,wherein:said short message being a short string of characters configuredto identify at least one of a base station, a repeater, and a radiobased network element that receives the short message, but not includinga digital signal processing mechanism to decipher a contents of any timeslot in the pattern of time slots in order to receive the short message.3. The device of claim 2, wherein:each time slot includes at least oneof speech, data, and nonusable information.
 4. The device according toclaim 3, wherein:at least one of the time slots being a half slot. 5.The device according to claim 4, wherein:each pattern of time slotsbeing an arrangement of particular time slots associated with differentshort messages, such that each pattern corresponds with a particularshort message.
 6. The device according to claim 1, wherein:saidshort-signaling mechanism includes more than one transmitter configuredto transmit on different frequencies while operating at a same time. 7.The device according to claim 1, wherein:said DECT signal beingconfigured to convey a long message without adversely affecting acapacity of the telecommunication system when the short-message istransmitted.
 8. The device according to claim 1, wherein:saidshort-signaling mechanism being hosted in a mobile unit configured toselect one of a base station, a carrier frequency and particular timeslots to be used for said short message, but subject to approval of thebase station.
 9. The device according to claim 8, wherein:in a simplexcommunication mode of operation, the base station selects and approvesthe carrier frequency and particular time slot to be used by the mobileunit.
 10. The device according to claim 9, wherein:the base stationallocates time slots using the short message.
 11. The device accordingto claim 1, comprising:a transmitter that hosts the short-messagesignaling mechanism and is configured to transmit said short message toa receiver that listens to only one channel per time slot such that inorder to detect an entirety of the short message, according to thepattern, the short message is repeated by the transmitter on as manyconsecutive frames as a number of carriers demanded in order to createthe short message such that the transmitter listens to only one carrierduring a particular frame, and then a next carrier at a next frame untilall frames have been listened to.
 12. The device according to claim 11,wherein:the short message being sent out continuously over apredetermined number of frames such that the transmitter listens to thepredetermined frames cylically, one carrier per frame.
 13. The deviceaccording to claim 11, wherein:the transmitter is configured not torepeat the entire short message during each frame by knowing whichlistening cycle a receiver uses for a particular time frame.
 14. Thedevice according to claim 1, wherein:said short-message signalingmechanism being configured to be included in a repeater such thatcommunications with the repeater does not adversely affect acommunication capacity of the system.
 15. The device according to claim1, further comprising:a receiver configured to receive a predeterminednumber of carriers in respective time slots so as to avoid decodinginformation contained in respective time slots.